Slice the sweet potato with the skin on into 1.5 cm dice. Put into a bowl of water to get rid of any bitterness.
Rinse the rice, put into a rice cooker, and add the sake. Top with water up to the 3-cup line. Add salt and mix lightly.
Put the sweet potato pieces on top of the rice, and leave to soak for 30 minutes.
Cook the rice as usual.
There's no need to add extra water because of the sweet potatoes. Just use the usual amount of water.
When the rice finishes cooking, let it steam for a while, then mix lightly.
Serve with sesame salt to taste.
Story Behind this Recipe
My mother taught me this recipe, and I adjusted the amounts.
Put the cut up sweet potato in a bowl of water right away, or it will turn black. Put the sake in the rice cooker with the rice, before filling with water. If you add it after filling up the water to the line, there will be too much liquid. Even with the sweet potato added, you can use the regular amount of water used to cook 3 rice cooker cups of rice. I sliced the sweet potato 1.5 cm thick, and then quartered the slices.